The present invention generally applies to the field of treatment of laminar flexible products, such as hides and skins, and particularly relates to a machine for conditioning such products by means of suitably processed air.
It is known that some kinds of laminar flexible products, e.g. industrial hides, absorb remarkable quantities of water and exhibit high moisture content that is unacceptable in semifinished or finished products.
Accordingly, such products must undergo a drying process by means of suitable machines and industrial plants.
It may be that when the above products are subjected to the above drying process, they result excessively or unevenly dried, thus loosing the necessary flexibility and handiness and as such being exposed to the risk of damage during the subsequent treatments.
It is further known that several products, such as industrial hides, must be subjected to finishing process involving impregnation on both sides with proofing agents having given physical and chemical properties. In such cases, if the products are dried on one side only or on one side at a time, they may give rise to a true barrier on the dried side that prevents removal of residual moisture from the inside of the products, thus causing unpleasant smells for long periods.
It is therefore understood that in several industrial fields, such as in tanning industry, there must be provided proper means for xe2x80x9cconditioningxe2x80x9d the products, meaning with this term controlling and adjusting accurately the residual humidity of the products according to their nature and thickness, as well as to the particular requirements of the semifinished or finished items.
Machines and plants for drying laminar flexible products with high moisture contents are known, e.g. vacuum drying machines of discontinuous type.
Such machines are provided with heating plates on which the products to be dried such as hides are accurately laid and subjected to high vacuum.
The moisture released by the products in the form of vapours is condensed and removed in the form of water.
The hides which undergo the above drying treatment may still have a residual moisture content comprised between 30% to 50%, which content for given applications can be either too high or too low.
Other drying systems are known which are of a continuous type, e.g. the chain drying plants in which the products to be dried are hung on an endless chain that unwinds continuously in open air along a path extending through the working areas intended for other processes, in such a manner to save space and labour time. While such known plants have a relatively low cost, they have the inconvenience of an extremely low flexibility due to the fact that the treatment is the same for all products and thus cannot be adapted to the thickness and nature of the different products hung on the chain. Moreover, the products stand for a very long thereby involving a remarkable blocking of capital.
Tunnel plants are similarly known wherein the products are caused to advance in a conduit through which a moderate air current flows, previously processed by suitable conditioners or moisture absorbers to provide a repeated and fair drying. In these known conditioning plants, the moisture present in the product is not eliminated in a uniform and controlled manner. Moreover, the treatment of the products is excessively slow and it does not allow to adapt to the production requirements that are more and more differentiated in extremely short times. Even in this case, an excessive capital blockage is involved with evident economical disadvantage.
From GB-A-2163450 an apparatus is known for treating leathers comprising all the features contained in the preamble of claim 1. In this known apparatus, the leathers under treatment are dried with heated air and stretched with endless rope loops advancing in a horizontal direction in a heating chamber. Nozzles located on the opposite sides of the leathers blow the heated air, while the leathers are moved forward by endless rope loops. A disadvantage of this known apparatus is that each nozzle is so shaped to blow air in a rather localised area and therefore the products under treatment are dried in insufficiently uniform manner. Moreover, the endless rope loops of this known apparatus extend only in one horizontal branch and therefore the leathers are conveyed through the heating chamber for only one length with relatively reduced air-drying action.
From GB-A-703391 an apparatus is known for treating and conditioning products such as textile or paper making use of air, steam or other gaseous fluids blown by groups of nozzle members located on both sides of the conveyed products. In this known apparatus there is provided no means for supporting and advancing the products under treatment in the passage between the groups of nozzle members. Moreover, each nozzle member has a pair of elongated orifices at its bottom wall. Finally, the products under treatment are conveyed through only one horizontal length in which there are provided the air nozzle members.
A primary object of the present invention is to provide a machine for the conditioning of laminar flexible products, particularly industrial hides, which allows to accomplish a controlled and uniform drying of the products on both sides thereof while preventing retention of moisture internally thereof.
A further object is to conceive a conditioning machine of laminar flexible products showing high rate and effectiveness of the treatment to thereby prevent immobilisation of large quantities of products and consequently of money, so as to obtain substantially planar and defect-free products.
A further object of the invention is to provide a conditioning machine having characteristics of high flexibility allowing to easily and promptly adjust the process parameters according to the products under treatment.
Another object is to provide a conditioning machine with relatively simple and compact structure so as to require a limited labour skill.
A further object is to provide a machine having a conditioning part as long as possible in a restricted space.
Still another object is to conceive a machine for the conditioning of leathers and similar products having a modular structure that is capable to adapt to particular requirements of bulk and of productivity in the room in which it is located.
These and other objects are achieved with a machine for the conditioning of leathers and similar laminar products in accordance with claim 1, which comprises at least one modular conditioning unit having an outer case with an inlet section for the products to be treated and an outlet section for the already treated products, means for the advancement of the products in a longitudinal direction between said inlet and outlet sections along a conditioning path, said advancement means comprising endless members adapted to face the opposite side of said products with respect to an advancement plane to firmly support and advance them along said conditioning path, means for circulating air within said conditioning unit, said air circulation means comprising two series of nozzles located on opposite sides of said advancement plane at regularly longitudinally spaced distance with respect to each other, said nozzles being provided with respective outlet ports for blowing air jets transversely of said advancement plane simultaneously on both sides of the products, characterised in that said outlet ports comprise for each nozzle a single elongated slit extending transversely with respect to said advancement direction, said endless members comprising a plurality of adjacent and straight lengths which are reciprocally superimposed and connected at one end thereof by reversing portions to define a substantially sinusoidal path, said series of nozzles being regularly distributed over all of said adjacent straight lengths.
Thanks to this arrangement, the products are subjected to a substantially uniform air blowing action while they are maintained in a substantially planar and even configuration with an extremely reduced shrinkage, thus allowing a quicker and more effective conditioning of the products.
In a preferred embodiment, each of the elongated slits has a substantially constant width and extends over almost the entire width of the conditioning unit.
Advantageously, the outlet ports of the nozzles may be arranged in substantially facing relationship, respectively in offset relationship with respect to the longitudinal direction.
The nozzles may comprise lateral walls converging towards said outlet ports and joined by a bottom wall substantially parallel to said advancement plane, where the outlet elongated slits are formed.